Cutter Insert Gum Modification Method And Appratus

ABSTRACT

Described herein are several methods and apparatuses for treating a cutter tool adapted to be used in tunnel boring operations. In one form, an initial cutter member blank is formed and heat treated prior to a laser cladding process. An alloy is often applied to the surface of the cutter blank adjacent to the cutting elements by the cladding process whereby the cladding process has insufficient heat transfer from the cladding process to reduce hardness properties of the inserts and/or the cutter blank. In one example a fabric-like material defines the region of the exterior hard surface.

RELATED APPLICATIONS

This application is a continuation of and claims priority benefit toU.S. patent application Ser. No. 13/653,315 filed Oct. 16, 2012. No newmatter has been added. U.S. patent application Ser. No. 13/653,315claims priority benefit to U.S. patent application Ser. No. 12/177,350incorporated herein by reference. U.S. patent application Ser. No.12/177,350 claims priority benefit of U.S. Provisional Ser. No.60/555,849, filed Mar. 23, 2004, U.S. Ser. No. 11/088,397 filed Mar. 23,2005, and U.S. Provisional Ser. No. 61/075,897 filed Jun. 26, 2008.

BACKGROUND OF THE INVENTION

a) Field of the Disclosure

The disclosure is generally related to applying laser cladding to thecutting structure of replaceable rings, “monoblock” assemblies, scraperblades, and other cutter tools.

b) Background Art

Tunnel boring machines often use rolling disc type cutters, scrapers,etc. on the front of their cutter heads to break and remove hardmaterials such as solid rock and embedded boulders. In certain instancesit is advantageous to use cutting structures comprised of a plurality ofhard buttons referred to as tungsten carbide Inserts (TCIs) which arecutting elements made usually of tungsten carbide and Cobalt in variousrelative concentrations embedded into a surrounding softer steel matrix.The TCI cutters stay sharper, longer than conventional cutter discscomprised only of steel. In order to more easily and economicallymachine a cavity in the steel matrix for the TCI button, the hardness ofthe steel may be limited to around 43 Rockwell Hardness maximum. Due toits relative softness, the material surrounding the button (the matrix)is worn away much faster than the TCI button. This differential wearcauses the buttons to become exposed and the support offered by thematrix erodes and eventually the buttons fall out in the course ofoperation. This is colloquially referred to as “gingivitis” because the“gums” (matrix) supporting the “teeth” (TCI buttons) wear down and theteeth get knocked out.

Therefore, it is an objective to address this erosion problem byaccurately applying an abrasive resistant material around and betweenthe buttons. It is hoped this layer will prevent the deterioration ofthe “gums” and allow the TCI cutter to survive longer. In one form thelayer is applied using a laser cladding process.

In the past manually applied hard facing has been applied to the flanksof TCI button cutting structure with unsatisfactory results. The manualprocess has lacked sufficient accuracy for localized heat application toapply material close to the button where the protection is most needed.The manual process also applies much more heat to the substrate thanlaser cladding such that the TCI buttons fell out or cracks ensuebecause the material became excessively brittle for the operatingenvironment. Therefore, it is proposed that laser cladding allows thelife of the TCI button cutter to be greatly extended.

In additional forms of tunneling, scraper-type blades are utilized wherein this similar type of scenario a scraper is inserted into a basematerial. In one form, it is more convenient to apply a surroundingsurface having a much higher hardness to protect these blade inserts. Inone form, a base matrix material can be applied to a scraper body, andholes can be drilled thereafter or prior to the application. Then thematerial can be hardened and the bits can be placed fitted therein, orthe bits can be fitted thereafter and have the material be hardened bysurgical application of heat, such as by laser cladding.

SUMMARY OF THE DISCLOSURE

The disclosure below recites several methods including a method andapparatus for providing a cutter tool having an outer region with aplurality of cavities with cutting elements fixedly positioned therein.The tool has a gum region that engages the cutting elements. The gumregion has a surface region with a hardened layer cladded to the surfaceregion where the hardened layer is cladded to the surface region whenthe cutter tool is preheated above 350° F. Heat is applied to an alloypowder to form the hardened layer whereby there is insufficient heattransfer to the cutting elements to affect the metallurgical hardnessproperties of the cutting elements. In general, the hardened layer andthe cutting elements have a Rockwell hardness at least 20 units greaterthan the gum region.

The method of treating a cutter ring described above generally firstcomprises providing a cutter tool that is heat treated with acircumferential region defining a plurality of cavities adapted toreceive cutting elements. Then cutting elements are inserted into thecavity regions. The tool may then be heat treated by heating the cuttertool to approximately 350° F.-650° F. Thereafter a laser claddingprocess is conducted whereby an alloy powder is applied to a cutter toolouter or gum surface adjacent to the cutting elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross sectional view of a cutter assembly;

FIG. 2 shows a portion of a cutter ring along the longitudinal axis;

FIG. 3 shows the upper detail region of FIG. 1 including a portion ofthe gum region on the circumferential portion of a cutter ring with acutting element insert shown in cross-section;

FIG. 4 shows the lower detail region of FIG. 1 including a portion ofthe gum region along the outer circumferential region of the cutter ringthat is interposed between two adjacent cutting element inserts;

FIG. 5 shows a laser cladding device for implementing a disclosedmethod;

FIG. 6 is a schematic view showing a nozzle for injecting powder coaxialwith the laser beam;

FIG. 7 shows the displacement of the coaxial nozzle and the laser beamfor resurfacing a surface region;

FIG. 8 and FIG. 9 show the displacement of a lateral nozzle and theassociated laser beam in a different embodiment;

FIG. 10 shows successive stages of cladding a surface region of a cutterring in cross-section through the insert;

FIG. 11 shows the internal structure of a gum region resurfaced, aftermachining and in transverse cross-section between the buttons;

FIG. 12 shows the movement of the focus of the laser beam in a firstembodiment;

FIG. 13 shows the movement of the focus of the laser beam in a secondembodiment;

FIG. 14 is a view in transverse section to a smaller scale of theinterface area of a laser deposit;

FIG. 15 shows an example of a scraper style insert;

FIG. 16 shows an example of abrasive wear upon a cutting element;

FIG. 17 shows an example of a material placed upon an underlyingsubstrate, such as a cutter blank;

FIG. 18 shows the material blended with the substrate and holes drilledtherein to the underlying substrate for placement of bits therein;

FIG. 19 schematically shows cutter bits placed in a cutting element suchas a cutter ring;

FIG. 20 shows an example of a coated cutting element.

FIG. 21 shows an example of a material prior to being placed upon anunderlying substrate, such as a cutter blank;

FIG. 22 shows the material blended with the substrate with holes drilledtherein to the underlying substrate for placement of bits therein;

FIG. 23 schematically shows cutter bits placed in a cutting element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the embodiment of FIG. 1 there is a portion of the cutterassembly 10 where an integral cutter ring/tool 12 is shown in a crosssectional view. The cutter ring 12 has an interior region 14 and acircumferential region 16. As shown in the lower portion of FIG. 1,cutting elements 18 are inserted at spaced locations around thecircumferential region 16. As shown in the upper portion of FIG. 1, thecircumferential region 16 further has a gum region 20 which is definedas the material surrounding the cutting elements 18. The gum region 20as shown in FIG. 2 is defined as the material that is adapted to holdthe cutting elements therein and is further described below. In the mostcommon form the cutting elements are pressed fit in to a cavity regionof the gum region 20 to form an interference fit. The gum region 20further comprises a surface region 22. It has been found that providinga surface to the gum area that has a sufficient hardness to reduce theamount of wear is advantageous and prevents gum erosion whereby thesurrounding support material is eroded causing the cutter inserts 18 tofall out in application. Therefore, the surface region 22 is hardened ina localized manner by application of a laser-clad material of thicknessbetween 30 thousands to ⅛ of an inch in a broad range and preferablyabout 1/16 of an inch. Of course the hardened layer could be thicker upto a quarter of an inch and even thicker in some applications asrequired.

Therefore, in one form of manufacture of the cutter ring 12, rawmaterial is provided and the raw material is rough machined to createthe center bore and sides to achieve the basic cross-sectional shape.Thereafter, the raw ring 12 is heat treated and then a plurality ofholes are drilled along the circumferential region 16 to providecavities adapted to receive the cutter inserts 18. Normally, theRockwell hardness of the cutter ring 12 at this stage in the manufactureprocess is approximately 32 to 44 (42-43 in the preferred range)Rockwell (Rockwell C scale) in the broader range so the aforementionedholes can be drilled out in an economical manner.

The cutting elements 18 are inserted in the cavity regions of theperimeter region 16. In general, the cutting elements 18 are pressfitted in the regions to provide an interference fit between theperimeter region 16 and the cutting elements 18. As shown in FIG. 4, theportion of the material in the perimeter region 16 that holds thecutting elements 18 therein is defined as the gum region 20 mentionedabove.

The entire assembly may then be preheated to approximately 350° F. to650° F. and a laser cladding process is then applied to the gum region20.

There will now be a description of a laser cladding process with initialreference to FIG. 5. It has been found that heating the cutter ring 12to above 650° runs the risk of having the cutting elements 18 fall outdue to the thermal expansion of the cutter ring.

Further, it may be advantageous to preheat the cutter tool and derivethe metallurgical advantages prior to application of the laser claddingprocess because the laser cladded hardened layer tends to act as athermal insulator to some degree, which inhibits subsequent heating ofthe gum region 20. Therefore, preheating the gum region 20 of the cutterring 12 (or in fact in general the entire cutter ring 12 and cuttingelements 18 are heated as well) has the benefit of the desiredmetallurgical treating of the gum region properly where it can be slowcooled after the application of hardened cladded layer.

FIG. 5 is a schematic representation of a laser cladding installationwhich can be used in implementing the invention. This installationcomprises a power laser 27 producing a beam 28 of coherent andmonochromatic light (laser). The beam 28 propagates in one directiononly, homogeneously, and has substantially only one wavelength. Ingeneral there is very little divergence of the beam.

In one form a set of mirrors 29 and 30 are provided to direct the beamonto a focusing head 31. The focusing head 31 directs the laser beamonto the surface to be resurfaced of the cutter ring 12. The focusinghead 31 is adapted to focus the laser beam so that the latter impingeson the cutter ring (not shown) in a small impact area 32 where in oneform the area is a diameter between about 0.5 and 5 millimeters wherethe cutter ring is to be positioned. A hemispheric dome shape-cuttingelement 18 is one form where the hard facing can be appliedcircumferentially around each button instead of going around the ringcutter 12.

A powder dispenser 52 constitutes a reservoir holding a powderedmaterial for laser cladding the cutter ring 12. This powder containsgrains of hard abrasion resistant material which remain solid whenexposed to the laser beam and grains of brazing alloy which melt whenexposed to the laser beam. In one form powder used is produced byTechnogenia S.A.™ of France as disclosed in U.S. Pat. Nos. 6,248,149 and5,580,472 that are hereby incorporated by reference.

The powder dispenser 52 is adapted to fluidize the powder by means of aneutral gas such as argon or helium and to convey it pneumatically to aspray nozzle 33 via powder feed lines 34. The spray nozzle 33 is adaptedto shape the fluidized powder leaving the nozzle into a convergent jetimpinging on the same impact area 32 on the cutter ring 12. Thefluidized powder jet leaving the nozzle must be as closely as possiblecoincident with the shape of the laser beam 28 in this area.

The powder dispenser 52 is of a type in which the mass flow rate ofpowder can be precisely controlled, in order to achieve excellentreproducibility and perfect regularity of the flow rate, whichparameters have a direct influence on the regularity and the quality ofthe resulting resurfacing.

The laser beam impinges on the surface of the gum region 30 to beresurfaced close to the vertical. The outlet orifice of the nozzle 33 ismaintained at a constant distance of approximately 10-40 millimetersfrom the surface to be resurfaced in one form.

In this embodiment, the cutter ring 12 is placed on a table 35 which maybe moved horizontally in two directions X and Y by drive meanscontrolled by a numerical controller 56. This causes the area of impact32 of the laser beam and of the powder leaving the spray nozzle 33 to bescanned over the surface of the gum region 20 to be resurfaced. In oneform this is accomplished by rotating the ring 12 about an axis and notnecessarily with an x-y table.

In the embodiment shown in FIG. 6 the spray nozzle 33 is of a first typewhich sprays coaxially with the axis I-I of the laser beam 28. Thefluidized powder moves in a helix coaxial with the laser beam 28 and thepowder jet 36 is concentrated in order to concentrate the area of impactof the powder onto the area of impact 32 of the laser beam 28 on thesurface region 22 to be resurfaced. This impact area 32 is positioned atthe surface region 22 as shown in FIG. 4.

FIG. 7 shows progressive laser cladding by displacement of the cutterring 12 in the direction 37. The area of impact 32 of the laser beam 28melts the brazing alloy powder, which is brazed to the surface region22, binding the grains of abrasion resistant material thereupon and,after cooling, progressively forming a deposit 58 on the top of theridge being resurfaced.

In the embodiment shown in FIG. 8, the spray nozzle 33 is a lateralspray nozzle which sprays the powder at a given angle to the laser beam28. The powder jet 38 is preferably in the vertical plane through thesurface region 22 to be resurfaced. The cutter ring 10 is scannedlongitudinally in alternate directions, as shown in FIG. 8.

As shown in FIG. 9 the spray nozzle 33 is directing the powder at agiven angle to the laser beam 28 on the surface region 22 that isinterposed between two adjacent cutting elements 18 along the perimeterouter edge of the cutter ring 12.

The energy of the laser beam 28 melts the surface of the surface region22 in the area of impact 32 and melts the brazing alloy powder. Thepowder therefore impinges partly melted on the surface of the surfaceregion 22. The alloy powder is trapped on the surface and melts furtherduring interaction of the laser beam 28 with the surface region 22, soforming a deposit.

FIG. 10 shows a schematic representation where the laser beam 28 has afocused distribution of light energy and the spray nozzle 33 is ejectingthe powder substrate to the surface region 22 which is forming ahardened layer. It should be noted that the laser 28 provides a verylocalized heat increase whereby the cutting element 18 is not overheatedand losing its material properties. It has been found that tungstencarbide degrades when the temperature reaches 900-1100 Fahrenheit. Ithas been found that the heat transfer to the cutting element 18 isminimal from the laser 28 whereby the cutting element 18 maintains itsmechanical properties to function properly in a tunnel boring operation.

FIG. 11 shows the laser cladding process occurring at the gum region 20at the portion of the surface region 22 interposed between two cuttingelements (not shown) on the circumferential ring portion. It isadvantageous to harden this area to prevent erosive wear between twoadjacent cutting elements.

To match the resurfacing exactly to the upper surface of the ridges, thelaser beam has to be controlled so that the area of impact 32 has adiameter substantially equal to the width of the ridge to be resurfaced.

The thickness of the deposit is between 30 thousands to ⅛ of an inch ina single pass. The processing speed can be from a few centimeters perminute to a few meters per minute, depending on the power of the laser27. A ridge can be resurfaced in a single pass if the thickness of thedeposit is a sufficient height.

After the laser cladding is applied no additional machining is needed tobe performed. Within the surface region 22 there are no defects inhomogeneity caused by formation of the multilayer deposit. Thedistribution of the hard abrasion resistant material, such as tungstencarbide, grains is uniform within the metal matrix, regardless of thenumber of layers deposited.

FIG. 12 shows a first method of adjusting the laser beam 28, with afocus F above the cutter ring 10 to be resurfaced. By varying thedistance between the focus F and the surface of the cutter ring 10 to beresurfaced the diameter of the area of impact 32 of the layer beam 28can be varied, as shown in the figure.

FIG. 13 shows a second method of adjusting the laser beam 28. In thissecond method the focus F is below the surface of the cutter ring 10 tobe resurfaced and varying the distance of the focus F from the surfaceof the cutter ring 10 also varies the size of the impact area 32 of thelaser beam 28.

At each 180° turn the position of the focus F is modified to compensatefor the height of the deposit previously formed, and thus to maintain aconstant diameter of the impact area 32.

The method in accordance with the invention has the advantage ofaccurate reproduction of the geometrical shape of the resurfaced ridges.The surface region 22 is affected minimally by the heating effect of thelaser beam during cladding and its distortion due to thermal expansionis thus extremely small or even negligible.

The bond between the cladding and the gum material 20 in FIG. 3 is verystrong, as it is achieved by surface melting of the substrate. This is ametallurgical bond which makes the cladding very strongly adherent. Theobtained surface is homogeneous, non-porous and produces only a smalldilution of the substrate. These features are shown in FIG. 14, whichshows a regular distribution of the grains 59 of tungsten carbide in themetal matrix 50 and a thin layer 51 bonding the metal matrix to the gumregion 20.

The grains of tungsten carbide 59 are not affected by the laser beam,the present method differing in this respect from plasma sputtering. Thegrains therefore retain all their mechanical properties, and inparticular their hardness is not reduced. This has the advantage that anabrasion resistant material based on generally spherical tungstencarbide grains can be used.

The very high rates of solidification obtained by virtue of the highlylocalized heat treatment produce a very fine microstructure within thematrix, and consequently excellent mechanical properties. In particular,the metal matrix in one form is based on nickel and chromium hashardness less than the hardened elements contained therein. Severaltypes of material to hold the carbide particles (hardened elements) canbe utilized. Nickel is a preferred element because of its tough andductile and cooperates with the spherical carbide particles withoutstress risers. In other words the matrix is soft compared to hardenedelements such as tungsten carbide spherical particles. By having thecutter ring 10 preheated to 350 to 650° F. the hardness of the heataffected zone (HAZ) directly under the cladding is about 43 to 47Rockwell hardness. The preheating prior to application of the lasercladding provides more uniform slow cooling. The goal is to reduce rateof cooling to prevent the HAZ brittleness. It is undesirable to formmartensite in the HAZ as it is brittle and prone to crack formation.Following the laser cladded process, the cutter ring, inserts, andhardened cladded layer may be cooled by being buried in vermiculite orsand or other slow cooling The preheating to 650° F. may prevent ahardened heat affected zone adjacent to the hardened layer. Because thehardened layer has insulating properties, it may be advantageous to havethe ring preheated so the thermal mass of the ring does not absorb theintense heat from the laser whereby causing a temperature gradient andundesirable metallurgical effects of the HAZ. The pre heating could behigher than 650° F. if precautions are taken so the cutting elements donot fall out during cladding. In fact the heating could go up to 900° F.(or the temperature limit of the cutting elements before undesirablemetallurgical changes take place) if such provisions are taken.

The coefficient of thermal expansion for the hardened layer is oftensomewhat less than steel which generally comprises the gum region 20 ofthe cutter ring 12. The preheating of the cutter ring 12 may havedesirable effects of reducing internal stress between the gum region andthe hardened layer. With steel as the underlying gum region having ahigher thermal expansion coefficient, when the unit cools, the centergum region will contract more than the hardface layer, thereby havingslight compressive annular stress in this hardface region and providinga higher circumferential compressive stress. This is indicated bypresent analysis, and this surface compressive stress is thought to bedesirable for reducing possible tension stress which causes the cracks.

When the cladding is conducted on an already heat treated surface atRockwell 42 (32-52 in the broader range) and then preheated, itgenerally does not crack after the cladding is applied on a drillingapplication. The forces in application may be sufficient to start acrack in the heat affective zone and spread throughout the whole ring ifthe hardness of the gum region is too high. It has been found that ifthe gum material is too hard the material forms propagating cracks whenthe cutters are in use in the rigorous cutting/drilling environment. Ifthe gum material 20 is too soft, or unprotected, the abrasive cuttingenvironment erodes the gum material 20 and the cutting elements 18 areforcefully removed or the cladded surface cracks because the underlyingsubstrate of the ring 12 has too much give and does not provide asufficient hard foundation.

It should be noted that the alloy powder can be directly inserted in thelaser beam as the laser passes the cutter ring perimeter surface.Alternatively, the alloy powder can be pre-applied, having the laserpass thereover. The Rockwell hardness of the cutting elements 18 islikely 20 to 30 (or 20 to 40 and above higher in a broader range) morethan the surrounding gum substrate area. Rockwell hardness for somecutting tools can be rated in the seventies. Such cutting elements suchas nitrided steels are at generally known to have an 80 Rockwellhardness rating so there is a generally broad range of 20 units greaterRockwell hardness from the cutters to the gum region and in some form 30and above to 40 and above units. It should be noted that there could bemultirow cutter inserts adapted to engage the earth in a cuttingoperation.

It should be noted that the gum region is traditionally a Rockwellhardness of 42 to have maximum abrasive wear resistance; however, givennow that the cladding operation provides abrasive resistance, theinterior gum region can be of a softer metal such as 32 Rockwell (lessthan 36 in one form) hardness which is very desirable to machine andwork with. Present analysis indicates that the Young's modulus of thesteel is approximately the same at a lower hardness whereby thedeflection of the gum region is similar given a compressive stress.Therefore, the hardened layer has a sufficient foundation to compressupon so there is a reduced chance of cracking.

It should be further noted that the cladding process can be used inother types of tools, such as scraper type tools or other tools withtungsten carbide cobalt braze material inserts. In general, scraper typetools can be used on soft ground for cutting therethrough oralternatively be used in conjunction with rolling tools. As shown inFIG. 15, there is an example of a worn scraper blade 200 having anon-cylindrical engagement tip 202 and a base 204. The base can beattached into a machined out slot within a scraper tool housing. Inoperation of scraper blades in a similar manner to the cutters describedabove, the surrounding support steel of the main body can wear out,having a “gingivitis” gum-like effect. Therefore, as shown in FIG. 20,supporting the steel with a protective layer of surgically applied hardfacing improves the overall life of the scraper. Present analysisindicates that a laser-applied hard facing bead can be applied within,for example 0.5 mm, of the carbide tips, because the heat affected zone(HAZ) is sufficiently small and the braze joint is not affected. Inconventional welding, heat goes deep into the part, which affects thebraze and can distort the slot or melt the brazing. With a laser, theheat is so directed that the application does not sufficiently affectthe metallurgy. In general, the base region 204/scraper body 242 is fitwithin a softer steel surrounding area and rigidly attached thereto.

In other forms, soft ground tunnel boring machine (TBM) tools can beutilized with the process of a laser-applied bead hard facing. Ingeneral, in one form there are two basic types of tools that can havethe process applied thereto. A first type of tool is smaller “straighttools” that are generally used on a flat face of a cutter head.Secondly, there are curved tools that can be used around the perimeterregion of a cutter head. In general primary wear occurs on the leadingedge and secondary wear occurs when the part drags through the earth.These cutter tools are designed to move bi-directionally, and thereforetools generally face one another wherein one is cutting in and anopposing side is being dragged.

Also disclose is the use of a fabric-like material, such as ConformaClad™, that can be utilized and draped over the part, molded thereto toform a hardened face. In this form, the steel could be coated incarbide, with the exception of the areas which the holes are drilled outto locate the cutter bits.

As shown in FIG. 16, there is an example of a curved scraping cutter. Aplurality of tungsten carbide inserts is indicated a 210. As can be seenin the portion 212, the inserts have worn away by an abrasive type wearreferred to as secondary wear. As shown in FIG. 17 there may be ageneral substrate material 220 such as a cutter blank, such as a softsteel. A braze-on fabric such as Conforma Clad™ 222 may be positionedthereon, having surfaces defining open regions (cavities) 224. As shownin the embodiment of FIG. 18, the openings 224 are provided to allow adrill bit or a similar type of metal excavating device to define theopenings 226. In general, the openings can be cylindrical holes or othershaped regions. Inserts 230 such as tungsten carbide cobalt inserts arefitted therein.

Now referring to FIG. 19, it can be appreciated that the cutter bits 230are fitted in the surfaces defining the openings 226. The fitting couldbe a press fit, brazing, or other type of fitting where the hardenedinserts are fixedly mounted therein.

Therefore, with reference to FIGS. 17-20, can be appreciated that in oneform the first step for producing the cutter tool is applying thepliable fabric-like material 222, which in one form can be the ConformaClad™ braze-on fabric. The pliable fabric-like material can be comprisedof a hard facing alloy which is operatively configured to liquefywherein the molten alloy will wick down into a layer of tungsten carbideparticles metallurgically bonding the hard particles to the cutter blankto clad thereto.

Now referring to FIG. 20, a main cutter scraper 240 has been fittedwithin the scraper body 242. Further, there are secondary protectivetungsten carbide-type inserts 244 which are configured to protectagainst secondary wear during the cutting process. The regions 246, 248and 250 adjacent the inserts 240/244 have a hard surface applied theretofor protecting the inserts 240/244 as well as the scraper body 242.

While the present invention is illustrated by description of severalembodiments and while the illustrative embodiments are described indetail, it is not the intention of the applicants to restrict or in anyway limit the scope of the appended claims to such detail. Additionaladvantages and modifications within the scope of the appended claimswill readily appear to those sufficed in the art. The invention in itsbroader aspects is therefore not limited to the specific details,representative apparatus and methods, and illustrative examples shownand described. Accordingly, departures may be made from such detailswithout departing from the spirit or scope of applicants' generalconcept.

Therefore I claim:
 1. A method of treating a cutter tool, the methodcomprising: a) identifying a gum region positioned in the outer portionof the cutter tool, b) employing laser cladding to the gum regionadjacent to cutting elements, c) whereas the cutting elements have ahardness higher than that of the surrounding gum region adjacent theretoand the heat transfer to the cutting elements from the laser claddingprocess is insufficient to materially alter the hardness of said cuttingelements and the gum region is more resistant to erosive wear.
 2. Themethod as recited in claim 1 whereby the cladding process applies acladding material at a thickness s greater than 0.030 of an inch.
 3. Themethod as recited in claim 1 whereby the heat transfer to the cuttingelements does not raise the temperature of the cutting elements above900° F.
 4. The method as recited in claim 1 further comprising the stepof brazing the cutting elements into cavities within the cutter tool. 5.The method as recited in claim 1 whereby a distance of a laser beam inthe laser cladding process to the gum region is adjusted to a consistentwidth during application on the gum region.
 6. A method of treating acutter tool, the method comprising the steps of: a) providing a cuttertool that is heat treated with an outer region defining a plurality ofcavities adapted to receive cutting elements, b) inserting cuttingelements into each of the cavities, c) engaging a laser cladding processwhereby an alloy powder is applied to the cutter tool outer surfaceadjacent to the cutting elements.
 7. The method as recited in claim 6where the Rockwell hardness of the cutter tool is between 32 and 44 whenforming the plurality of cavities.
 8. The method as recited in claim 7whereby the cutting elements are press fit into the cavity regions. 9.The method as recited in claim 6 whereby the alloy powder is introducedinto the laser as it passes along the cutter tool perimeter surface. 10.The method as recited in claim 6 whereby the alloy powder is positionedon the cutter tool outer surface and the laser transfers heat thereto.11. The method as recited in claim 6 whereby the material immediatelysurrounding the cutting elements in the cutter tool defines a gum regionhaving a hardness at least 20 Rockwell units lower than the cuttingelements.
 12. The method as recited in claim 11 whereby the Rockwellhardness of the laser cladded layer on the cutter tool outer surface isat least 20 Rockwell hardness higher than the cutter tool.
 13. A cuttertool comprising: a. a perimeter region with a plurality of cavities withcutting elements fixedly positioned in said cavities, b. the cutter toolhaving a gum region with a plurality of cavities therein retaining saidcutting elements, c. the gum region having a surface region, d. ahardened layer cladded to the surface region where the hardened layer iscladded to the surface region when the cutter tool is preheated above350° F. and heat is applied to an alloy powder to form the hardenedlayer whereby the cutting elements are not affected by the heat isapplied to an alloy powder and the metallurgical hardness properties ofthe cutting elements is preserved.
 14. The cutter tool as recited inclaim 13 where the temperature of the cutting elements during the heattransfer to the alloy powder does not increase above 900° F.
 15. Thecutter tool as recited in claim 13 where the Rockwell hardness of thecutting elements in the hardened layer is at least 30 units greater thanthe gum region.
 16. The cutter tool as recited in claim 15 where thesurface region is comprised of a matrix composition mixed with atungsten carbide material.
 17. The cutter tool as recited in claim 13where the hardened layer is not more than ⅛ of an inch in thickness. 18.The cutter tool as recited in claim 16 where the Rockwell hardness ofthe cutter tool is not more than 44 when forming the plurality ofcavities in the gum region.
 19. The cutter tool as recited in claim 16where the cutting elements are placed in the cavities after the hardenedlayer is formed.
 20. The cutter tool as recited in claim 16 where thecutting elements are placed in the cavities prior to the application ofalloy powder to form the hardened layer.